This invention relates to an electrical terminal clamp for establishing an electrically conducting clamping connection between an electrically conductive wall of a housing of the terminal clamp and an insulated electrical wire being introduced into the housing along its electrically conductive wall, a clamping member being rotatably mounted in the housing for turning movement in the longitudinal direction of the wire in such a manner that during such turning movement relative to the wall, upon baring and contactual engagement of the wire, a clamping slot is formed which is narrower than the diameter of the conductor of the wire.
A terminal clamp of this kind is known, comprising a clamping member which is rotatably mounted relative to a cylindrical wall and is constructed with a cutting edge or a saw-toothed cam, by means of which the insulation is ruptured before the clamping is completed and contact is established via the cutting edge or saw-toothed cam or via a zone of the clamping member adjacent the cutting edge or the saw-toothed cam. Where a saw-toothed cam is used, the peeling-off of the insulation layer will be accompanied by an accumulation of insulating material between the saw-teeth, and this accumulated insulating material will exert a pressure counter-acting the contact pressure which must therefore be chosen sufficiently high for overcoming this counter-pressure. Moreover, there is a risk that a cutting edge or a saw-toothed cam, in the process of removing the insulation or afterwards, may damage the naked conductor of the wire and form notches therein which may initiate rupture and thereby destruction of the electrical connection. Terminal clamps in which the insulation is peeled off the wire are not suitable for the re-establishment of electrical connection with a previously used wire end, first because the establishment of contact takes place at the same point of the wire end as previously, whereby the contact pressure generally becomes lower and, second, because the terminal clamp must each time be emptied of previously peeled-off insulating material, which complicates the operation, not least if the terminal clamp is fixedly mounted or is integral with other terminal clamps.
A terminal clamp is also known in which the clamping member is constructed with a rounded pressing portion which upon turning of the clamping member locally flattens the wire over a relatively long length so that the conductor of the wire is pressed against a conducting surface to establish contact with same, the baring of the wire taking place by causing the conductor of the wire to penetrate the insulation over the noted relatively long length of the wire. Since the rounded pressing member engages the conductor over a relatively long length thereof, its dimension in the direction of the conductor must be greater than the diameter of the latter, and the same applies to its radius of curvature. As a consequence, a relatively high force is required for the flattening of the wire and for causing the conductor to penetrate the insulation and to establish the metallic contact. This again means that a relatively great torque will be required for turning the clamping member so that it will be necessary to use a lever for producing the torque required for the establishment of contact with even a single wire. Also in this case the re-establishment of the connection will result in a poorer contact unless the previously used wire end is cut off. Owing to the high pressure required for the operation of establishing contact, each such operation will give rise to considerable wear unless the movable parts are lubricated each time.